Authentic surface structures under reaction conditions determine the activity and selectivity of electrocatalysts, therefore, the knowledge of the structure‐activity relationship can facilitate the design of efficient catalyst structures for specific reactivity requirements. However, understanding the relationship between a more realistic active surface and its performance is challenging due to the complicated interface microenvironment in electrocatalysis. Herein, we proposed a standard research paradigm to effectively decipher the structure‐activity relationship in electrocatalysis, which is exemplified in the CO 2 electroreduction over SnO 2. The proposed practice has aided in discovering authentic/resting surface states (Sn layer) of SnO 2 accountable for the electrochemical CO 2 reduction reaction (CO 2RR) performance under electrocatalytic conditions, which then is corroborated in the subsequent CO 2RR experiments over SnO 2 with different morphologies (nanorods, nanoparticles, and nanosheets) in combination with in situ characterizations. This proposed methodology is further extended to the SnO electrocatalysts, providing helpful insights into catalytic structures. It is believed that our proposed standard research paradigm is also applicable to other electrocatalytic systems, in the meantime, decreases the discrepancy between theory and experiments, and accelerates the design of catalyst structures that achieve sustainable performance for energy conversion.